The paper's first author is Dr Gene Bowman from the Departments of Neurology and Public Health and Preventive Medicine at Oregon Health & Science University in Portland, and a member of the American Academy of Neurology. He and his colleagues describe three sets of findings:
- Elderly people with diets high in several vitamins or omega 3 fatty acids were less likely to have the brain shrinkage that usually accompanies Alzheimer's disease than people whose diets were low in those nutrients.
- Those whose diets were high in omega 3 fatty acids and in vitamins C, D, E and the B vitamins were also more likely to score better on tests of mental ability than those whose diets were low in those nutrients.
- Those whose diets were high in trans fats were more likely to have brain shrinkage and perform less well on thinking and memory tests than those whose diets were low in trans fats.
B vitamins and antioxidants C and E are primarily found in fruits and vegetables, except for B12, which mostly comes from animal products, although it is also present in fortified breakfast cereals. Trans fats are primarily found in fast, packaged, fried and frozen food, many baked goods and margarine spreads.
The study is thought to be the first to measure several nutrient biomarkers in the blood as a way to examine links between diet and memory, thinking and brain volume.
Until now, other studies have only examined or or two nutrients at a time, or have used data from diet questionnaires, which rely on people's memory of what they eat and do not account for how efficiently their bodies retain the nutrients, a particular problem in the elderly.
For the study, Bowman and colleagues recruited 104 elderly people of average age 87 who had few risk factors for impaired memory and thinking. From participants' blood tests the researchers measured 30 different nutrient biomarkers. All the participants also completed tests of memory and thinking, while 42 of them also underwent MRI scans that measured their brain volume.
The results showed that overall the participants' diets were healthy, but 25% were lacking in vitamin D and 7% were deficient in vitamin B12.
Bowman told the press that their results showed a significant amount of the variation in brain volume and scores on the thinking and memory tests were tied to levels of nutrients biomarkers.
On the thinking and memory tests, the nutrient levels accounted for 17% of the variation in the scores, while 46% of the variation was tied to other factors such as age, number of years of education and blood pressure.
For brain volume, the nutrient levels accounted for 37% of the variation.
"These results need to be confirmed, but obviously it is very exciting to think that people could potentially stop their brains from shrinking and keep them sharp by adjusting their diet."
Co-author Dr Maret Traber, a principal investigator with the Linus Pauling Institute at Oregon State University said their findings are based on average people eating average American diets:
"The vitamins and nutrients you get from eating a wide range of fruits, vegetables and fish can be measured in blood biomarkers."
"I'm a firm believer these nutrients have strong potential to protect your brain and make it work better," she said, adding that anyone "considering a New Year's resolution to improve their diet, this would certainly give them another reason to eat more fruits and vegetables".
Funds from the National Institutes of Health, the National Institute on Aging and National Center for Complementary and Alternative Medicine and the U.S. Department of Veteran Affairs, Portland VA Medical Center, helped pay for the research.